Ultrastructural In Situ Hybridization

Abstract

In 1969, the in situ hybridization (ISH) technique was introduced for the detection of ribosomal RNA gene products (1, 2). Many investigators have since improved this technique to identify specific genes or gene products in cells. The development of synthetic oligonucleotide probes, which could be easily designed and produced, contributed greatly to the refinement of ISH (3). Nonradioactive synthesized oligonucleotide probes labeled with biotin or digoxigenin were introduced for the detection of ISH signals (4,10). ISH under a brightfield light microscope (LM-ISH) has since become a widely used method for examining the tissue distribution and expression of mRNA. The LM-ISH method is lacking in the resolution required for studies on the spatial relationship between mRNA and the protein product. This type of information can only be provided by ultrastructural studies.